For rods with a rectangular cross section composed of an elastically isotropic material, the bending and twisting stiffness are [1]},
\(\begin{aligned}EI_1=\tfrac{1}{12} E w^3 t\,,\; EI_2=\tfrac{1}{12} E w t^3 \,,\;GJ=\lambda G w t^3=\lambda \frac{E}{2(1+\nu )} w t^3 \, ,\end{aligned}\) 
